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crash_dump.c

/*
 * Routines for doing kexec-based kdump.
 *
 * Copyright (C) 2005, IBM Corp.
 *
 * Created by: Michael Ellerman
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 */

#undef DEBUG

#include <linux/crash_dump.h>
#include <linux/bootmem.h>
#include <linux/lmb.h>
#include <asm/code-patching.h>
#include <asm/kdump.h>
#include <asm/prom.h>
#include <asm/firmware.h>
#include <asm/uaccess.h>

#ifdef DEBUG
#include <asm/udbg.h>
#define DBG(fmt...) udbg_printf(fmt)
#else
#define DBG(fmt...)
#endif

/* Stores the physical address of elf header of crash image. */
unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;

#ifndef CONFIG_RELOCATABLE
void __init reserve_kdump_trampoline(void)
{
      lmb_reserve(0, KDUMP_RESERVE_LIMIT);
}

static void __init create_trampoline(unsigned long addr)
{
      unsigned int *p = (unsigned int *)addr;

      /* The maximum range of a single instruction branch, is the current
       * instruction's address + (32 MB - 4) bytes. For the trampoline we
       * need to branch to current address + 32 MB. So we insert a nop at
       * the trampoline address, then the next instruction (+ 4 bytes)
       * does a branch to (32 MB - 4). The net effect is that when we
       * branch to "addr" we jump to ("addr" + 32 MB). Although it requires
       * two instructions it doesn't require any registers.
       */
      patch_instruction(p, PPC_NOP_INSTR);
      patch_branch(++p, addr + PHYSICAL_START, 0);
}

void __init setup_kdump_trampoline(void)
{
      unsigned long i;

      DBG(" -> setup_kdump_trampoline()\n");

      for (i = KDUMP_TRAMPOLINE_START; i < KDUMP_TRAMPOLINE_END; i += 8) {
            create_trampoline(i);
      }

#ifdef CONFIG_PPC_PSERIES
      create_trampoline(__pa(system_reset_fwnmi) - PHYSICAL_START);
      create_trampoline(__pa(machine_check_fwnmi) - PHYSICAL_START);
#endif /* CONFIG_PPC_PSERIES */

      DBG(" <- setup_kdump_trampoline()\n");
}
#endif /* CONFIG_RELOCATABLE */

/*
 * Note: elfcorehdr_addr is not just limited to vmcore. It is also used by
 * is_kdump_kernel() to determine if we are booting after a panic. Hence
 * ifdef it under CONFIG_CRASH_DUMP and not CONFIG_PROC_VMCORE.
 */
static int __init parse_elfcorehdr(char *p)
{
      if (p)
            elfcorehdr_addr = memparse(p, &p);

      return 1;
}
__setup("elfcorehdr=", parse_elfcorehdr);

static int __init parse_savemaxmem(char *p)
{
      if (p)
            saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;

      return 1;
}
__setup("savemaxmem=", parse_savemaxmem);


static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
                               unsigned long offset, int userbuf)
{
      if (userbuf) {
            if (copy_to_user((char __user *)buf, (vaddr + offset), csize))
                  return -EFAULT;
      } else
            memcpy(buf, (vaddr + offset), csize);

      return csize;
}

/**
 * copy_oldmem_page - copy one page from "oldmem"
 * @pfn: page frame number to be copied
 * @buf: target memory address for the copy; this can be in kernel address
 *      space or user address space (see @userbuf)
 * @csize: number of bytes to copy
 * @offset: offset in bytes into the page (based on pfn) to begin the copy
 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
 *      otherwise @buf is in kernel address space, use memcpy().
 *
 * Copy a page from "oldmem". For this page, there is no pte mapped
 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
 */
ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
                  size_t csize, unsigned long offset, int userbuf)
{
      void  *vaddr;

      if (!csize)
            return 0;

      csize = min(csize, PAGE_SIZE);

      if (pfn < max_pfn) {
            vaddr = __va(pfn << PAGE_SHIFT);
            csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
      } else {
            vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
            csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
            iounmap(vaddr);
      }

      return csize;
}

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